<?php

/*
 * XXTEA encryption arithmetic library.
 *
 * Copyright (C) 2006 Ma Bingyao <andot@ujn.edu.cn>
 * Version:      1.5
 * LastModified: Dec 5, 2006
 * This library is free.  You can redistribute it and/or modify it.
 */

function long2str($v, $w)
{
	$len = count($v);
	$n = ($len - 1) << 2;
	if ($w)
	{
		$m = $v[$len - 1];
		if (($m < $n - 3) || ($m > $n))
		{
			return false;
		}
		$n = $m;
	}
	$s = array();
	for ($i = 0; $i < $len; $i++)
	{
		$s[$i] = pack("V", $v[$i]);
	}
	if ($w)
	{
		return substr(join('', $s), 0, $n);
	}
	else
	{
		return join('', $s);
	}
}

function str2long($s, $w)
{
	$v = unpack("V*", $s.str_repeat("\0", (4 - strlen($s) % 4) & 3));
	$v = array_values($v);
	if ($w)
	{
		$v[count($v)] = strlen($s);
	}
	return $v;
}

function int32($n)
{
	while ($n >= 2147483648)
	{
		$n -= 4294967296;
	}
	while ($n <= -2147483649)
	{
		$n += 4294967296;
	}
	return (int) $n;
}

function xxtea_encrypt($str, $key)
{
	if ($str == "")
	{
		return "";
	}
	$v = str2long($str, true);
	$k = str2long($key, false);
	if (count($k) < 4)
	{
		for ($i = count($k); $i < 4; $i++)
		{
			$k[$i] = 0;
		}
	}
	$n = count($v) - 1;

	$z = $v[$n];
	$y = $v[0];
	$delta = 0x9E3779B9;
	$q = floor(6 + 52 / ($n + 1));
	$sum = 0;
	while (0 < $q--)
	{
		$sum = int32($sum + $delta);
		$e = $sum >> 2 & 3;
		for ($p = 0; $p < $n; $p++)
		{
			$y = $v[$p + 1];
			$mx = int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
			$z = $v[$p] = int32($v[$p] + $mx);
		}
		$y = $v[0];
		$mx = int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
		$z = $v[$n] = int32($v[$n] + $mx);
	}
	return long2str($v, false);
}

function xxtea_decrypt($str, $key)
{
	if ($str == "")
	{
		return "";
	}
	$v = str2long($str, false);
	$k = str2long($key, false);
	if (count($k) < 4)
	{
		for ($i = count($k); $i < 4; $i++)
		{
			$k[$i] = 0;
		}
	}
	$n = count($v) - 1;

	$z = $v[$n];
	$y = $v[0];
	$delta = 0x9E3779B9;
	$q = floor(6 + 52 / ($n + 1));
	$sum = int32($q * $delta);
	while ($sum != 0)
	{
		$e = $sum >> 2 & 3;
		for ($p = $n; $p > 0; $p--)
		{
			$z = $v[$p - 1];
			$mx = int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
			$y = $v[$p] = int32($v[$p] - $mx);
		}
		$z = $v[$n];
		$mx = int32((($z >> 5 & 0x07ffffff) ^ $y << 2) + (($y >> 3 & 0x1fffffff) ^ $z << 4)) ^ int32(($sum ^ $y) + ($k[$p & 3 ^ $e] ^ $z));
		$y = $v[0] = int32($v[0] - $mx);
		$sum = int32($sum - $delta);
	}
	return long2str($v, true);
}